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ISC Class XI Notes 2025 : Chemistry

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CHAPTER-1 SOME BASIC CONCEPTS OF CHEMISTRY TOPIC-1 Introduction to Chemistry and Matter Revision Notes Chemistry is the branch of science which deals with the study of materials, their preparations, their properties, their accurate super microscopic structures, their mutual interactions, and their uses in all possible walks of life. The main branches of chemistry are inorganic chemistry, organic chemistry, physical chemistry and analytical chemistry. (i) Inorganic Chemistry: All metals, non- metals their properties, extraction, their compounds- preparation and properties of those compounds, all is studied in this branch. (ii) Organic chemistry : This branch deals with carbon compounds and its derivatives: aliphatic hydrocarbon, its derivatives, benzene and its derivatives, carbohydrates, proteins, fats etc. (iii) Physical chemistry: This branch deals with logical explanation of rules, theories, hypothesis and laws. It also explains nuclear processes and spectroscopy. (iv) Analytical chemistry: This branch deals with qualitative and quantitative analysis of solids, liquids and mixtures. Few other important branches of Chemistry are: Bio-chemistry, Chemical Physics, Industrial Chemistry, Agricultural Chemistry, Pharmaceutical Chemistry. Particulate Nature and Classification of matter: l The entire universe is made up of matter and energy. l Matter was believed to be made up of discrete particles, called matter. l John Dalton proposed atomic theory. l J.J.Thomson challenged atomic theory and proved that atoms are not indivisible using discharge tube experiments. l The model of an atom given by Neil Bohr successfully explains the spectrum of hydrogen. Classification of Matter: l Matter can be classified in two ways: Physical and Chemical classification of matter l On the basis of physical state, matter can be classified into : (i) Solid state: It has definite shape and possess the definite volume. The molecules are closely packed. They vibrate along their axis. They are hard and rigid. (ii) Liquid state: They have definite volume but not the definite shape. Intermolecular distance is more as compared to those in solids. They acquire the shape of the container. (iii) Gaseous state: It possess neither definite shape nor definite volume. The molecules are free to move anywhere. Intermolecular distances are quite high. They can be easily compressed. Chemically matter can be classified into pure substances and mixtures. Pure substances are further classified into elements and compounds. Elements: l Elements are the constituents of pure substance. 2 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI l Oxygen, silicon, aluminium, iron and calcium constitute about 90% of the earth s crust. l Elements are further classified into: metals, non metals and metalloids Compounds: l They are made up of two or more elements. l The properties of compounds are quite different from those of its constituents elements. l Compounds are further classified into: (i) Inorganic Compounds and (ii) Organic Compounds (i) Inorganic Compounds: Are obtained from non- living sources. (ii) Organic Compounds: These are compounds of carbon and have organic nature. Mixtures: l It shows the properties characteristics of its components. l It depends on the ratio in which the constituent elements are mixed. l Mixture can further be classified as: homogeneous and heterogeneous mixture. Properties of matter and their measurements l Properties of matter can be classified as physical and chemical properties. l A modern system of unit called as metric system was adopted by India in 1957. l The accuracy of a measurement represents the extent to which an experimentally measured value is close to the true value. l The two possible types of physical quantities are: Discrete variables and continuous variables. Know the Definitions Element: An element may be defined as pure substance which can neither be decomposed into, nor can be synthesized from simpler substances by ordinary physical or chemical methods. Metalloids: The elements which possess properties characteristics to both metals and non-metals are called metalloids. Compound : A compound may be defined as substance obtained by the chemical combination of two or more elements in a definite proportion by mass. Mixtures : It may be defined as the combination of two or more elements or compounds in any arbitrary ratio which retains the identity of the compounds being mixed. Homogeneous mixture : When the components of a mixture are distributed uniformly through- out the sample i.e. all components are present in the same ratio in all parts of it, it is said to be homogenous mixture. Heterogenous mixture: When the components of a mixture are not distributed uniformly, it is said to be heterogenous mixture. Physical properties are those properties which can be measured without altering the identity or composition of the substance. Chemical properties are those properties which require a chemical change and involve a change in the chemical composition of the substance. Discrete variables: The quantities which can be measured with certainty are called discrete variables. Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 3 Continuous variables: The physical quantities involving uncertainty in their measurements are called as Continuous variables. TOPIC-2 Dalton s Atomic Theory Revision Notes John Dalton proposed that matter is made of extremely small discrete particles called atoms. Lavoisier is regarded as the Father of Chemistry. According to Law of conservation of mass, during any physical or chemical change, the total mass of the products obtained is always equal to the total mass of reactants taken at the beginning. During any physical or chemical change, the matter is neither created nor destroyed. However, it may change from one form to another. Law of constant composition was also known as law of definite proportion. The compounds in which atoms of a molecules are not present in simple whole number ratio are known as stoichiometric compounds AVOGADRO S HYPOTHESIS: l Formation of hydrogen chloride and formation of water vapours can be explained on the basis of Avogadro s Law. l Hydrogen and oxygen molecules are diatomic. l Atom is the smallest particle of an element and is the unit of chemical reactions. It may or may not have independent existence. l Molecule is the smallest particle of the substance (element or compound) which can exist independently. l Depending upon the types of elements present in them, molecules can be classified as : Homoatomic and heteroatomic molecules. Know the Definitions Isotopes : Isotopes of an element are those species which possess similar atomic number but different atomic masses. eg. Carbon has three isotopes, C12, C13 and C14. Law of constant composition: A chemical compound, no matter from which source it is obtained, always contains the same elements combined together in the same definite proportion by mass. eg. Water is composed of two elements hydrogen and oxygen in the ratio 1 : 8 by mass. Pure water obtained from any source, eg. hand pump, well or artificially prepared in laboratory, always contain hydrogen and oxygen in the ratio 1: 8 by mass. Law of multiple proportion: When two elements combine to form two or more compounds, then the different mass of one element, which combine with a fixed mass of other element, bear a simple whole number ratio with one another. Law of reciprocal proportions: When two elements combine to form two or more compounds, then the different mass of one element, which combine with a fixed mass of other element, bear a simple whole number ratio with one another. Gay Lusaac s law of combining volumes: According to Gay Lussac s Law of Gaseous Volumes, When gases combine or are produced in a chemical reaction they do so in a simple ratio by volume, provided all gases are at the same temperature and pressure. Berzelius hypothesis: Under identical conditions of temperature and pressure, equal volume of all gases contain equal number of atoms. Avogadro s hypothesis: Under identical conditions of temperature and pressure, equal volumes of all gases contain equal number of molecules. Atomicity: Atomicity of an elementary substance is defined as the number of atoms present in one molecule of that substance. Homoatomic molecules: When a molecule is composed of atoms of the same element, it is said to be monoatomic element. eg. He, H2, N2, O3 and P4 etc. Heteroatomic molecules : When a molecule is composed of atoms of more than one type of elements, it is said to be heteroatomic element. eg. molecules like HCl, H2O, NH3 and CO etc. 4 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI TOPIC-3 Equivalent Weights Revision Notes Equivalent weight or equivalent mass of a substance is the number of parts by mass of the given substance which combines with or displaces directly or indirectly 1.008 parts by mass of hydrogen, or 8 parts by mass of oxygen, or 35.5 parts by mass of chlorine. Equivalent weight is just a number and has no units. Equivalent element of an element is inversely proportional to its valency. Unit of electrochemical equivalent is gC-1. According to Avogadro s hypothesis, under similar conditions of temperature and pressure, equal volume of all gases contain equal number of molecules. If the substance has same molecular formula as its chemical formula, the molecular mass of the substance will be same as its formula mass. The different methods for the determination of molecular masses of gases are : Molar Volume Method, Regnault s Method, Diffusion Method and Ideal Gas Equation Know the Definitions Faradays law of electrolysis: First law: The amount of substance liberated (or deposited) at a particular electrode during electrolysis is directly proportional to the quantity of electricity ( total charge) passed in the solution. Second Law: When the same quantity of electricity is passed through the solutions of different electrolytes connected in series , the masses of the substance liberated (or deposited)at the electrodes are directly proportional to their equivalent weights. Electrolysis: Electrolysis may be defined as the process which leads to a chemical change on the passage of electricity through an electrolyte present either in the dissolved state or in the molten state. Basicity of an acid : The basicity of an acid is defined as the number of H+ ions furnished by one molecule of the acid in solution. Acidity of base: Acidity of a base is defined as the number of OH ions furnished by one molecule of the base in solution. Gram equivalent weight: The mass in grams of a substance numerically equal to its equivalent weight is called its gram equivalent weight. Graham s Law of diffusion: At constant temperature and pressure, the ratio of diffusion of gas is inversely proportional to the square root of its density. Know the Formulae Equivalent weight of an element = Atomic mass Valency Equivalent weight of a normal salt = Equivalent weight of an acid salt = Equivalent weight of an acid = Formula wt. of the salt Total charge on cationic part Formula wt. of the salt No. of replaceable hydrogen atom Molecular weight of the acid Basicity of the acid Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI Equivalent weight of a base = Molecular weight of the base Acidity of the base Equivalent weight of an oxidant or reductant = Equivalent weight = [ 5 Atomic mass Valency Formula mass No. of electrons gained or lost by one molecule Atomic mass Equivalent weight = Oxidation state Number of gram molecules = Vapour density = mass in grams molecular mass mass of known volume of the gas at a particular temp and prressure mp and pressure mass of the same volume of hydrogen at the same tem PV = n RT TOPIC-4 Volumetric Calculations Revision Notes Titration involves the addition of a solution of known strength to a definite volume of a solution of unknown strength until the reaction between two is just complete. Molarity represents the concentration of solution in mol L 1. Formality changes with change in temperature. Molality of solution does not change with temperature. Mole fraction is independent of temperature. Stoichiometry of Chemical Reactions: Stoichiometric ratio is the simplest whole number ratio of moles of reactant and products involved in the reaction. A chemical equation is the brief representation of a chemical reaction in terms of chemical formulae of reactants and products in stoichiometric ratio. A chemical equation must fulfil the following conditions: It should be consistent with the true chemical reaction under consideration. It should be molecular. It should be balanced. Know the Definitions Unknown solution: The solution whose strength is not known and is desired to be estimated by titration is known as unknown solution. Known solution or standard solution: The solution whose strength is accurately known is called as known solution. Mass percentage: It is defined as the mass of the solute in grams dissolved per 100g of solution. Molarity: The number of moles of solute dissolved per litre of the solution at a particular temperature is called the molarity of the solution at that temperature. Formality: The number of gram formula mass of an ionic solute dissolved per litre of the solution at a particular temperature . Molality: It is defined as the number of moles of solute dissolved per 1000g (or 1 kg) of the solvent. Normality: The number of gram equivalents of the solute dissolved per litre of a solution at a particular temperature is called normality of solution. 6 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI Chemical Equation: A chemical equation is the brief representation of a chemical reaction in terms of chemical formulae of reactants and products in stoichiometric ratio. Limiting reagent: It is the reactant which get completely consumed in the chemical reaction under consideration and whose amount limits the amount products formed in the reaction. Know the Formulae Mass percentage of solute = mass of solute mass of solute 100 = 100 mass of solute+mass of solvent mass of solution Mass percentage of solute = volume of solute 100 volume of solution Molarity = Number of moles of solute Volume of the solution in litres Formality of a solution = Molality = No. of gram formula mass of the solute Volume of the solutio on in litres Number of moles of solute Mass of the solvent in kg Normality = No. of gram equivalents of solute Volume of the solution in n litres Molarity molecular mass of solute = Normality equivalent mass of solute Mole fraction = No. of moles of the given component Total number of moles in n the solution Number of gram equivalents = Normality Volume (in cm 3 ) 1000 Normality reaction = N1V1 = N2V2 ll CHAPTER-2 STRUCTURE OF ATOM TOPIC-1 Subatomic particles Revision Notes The term parmanu was first used by Maharishi Kanad. John Dalton proposed a classical model of an atom The experiments revealed that atoms consists of subatomic particles called fundamental particles. The three most important subatomic particles are : electron, proton and neutron. Evidence for Electrical Nature of Matter: l Michael Faraday showed that electricity could be passed through the solutions of certain substances called as electrolytes. l When electric current was passed through the solution of an electrolyte, some changes occurred in electrolyte. These changes were called as electrolysis. l Faraday s experiment revealed that matter is electrical in nature. l Stoney named the discrete particles of electricity as electrons. Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 7 Know the Terms Mass number : The sum of total number of protons and neutrons present in the nucleus of an atom is called the mass number of that atom. Know the Formulae Mass number (A) = Number of protons + Number of neutrons = Number of nucleons TOPIC-2 Electromagnetic Radiation and Atomic Spectra Revision Notes Newton proposed a theory known as Corpuscular theory according to which light is composed of tiny particles called as corpuscles. The theory explained about phenomenon of reflection and refraction but failed to explain interference and diffraction. Dual Nature of Light: l Light is composed of stream of particles. l The phenomenon like diffraction, interference, polarisation of light could be explained on the basis of wave theory of light. Atomic Spectra: l When sunlight passes through a prism, a series of coloured band is observed. l Continuous spectrum is due to the collective behaviour of a large number of interacting atoms. l Based on frequencies, atomic spectra are of two types: Emission Spectra and Absorption Spectra. l Electromagnetic waves do not require any medium for propagation. Know the Definitions The point of maximum amplitude is called crest. The point of minimum amplitude is called trough. Wavelength: The distance between two consecutive crests or two consecutive troughs is called wavelength. Frequency : The number of waves passing through a reference point in one second is called the frequency. Velocity : The distance travelled by a wave in one second is called the velocity of the wave. Wave number : The number of waves which can be accommodated in a unit length is called the wave number. Amplitude : The height of a crest or the depth of a trough from the line of propagation of the wave is called amplitude. Radiant energy is emitted or absorbed discontinuously in the form of small energy bundles or energy packets called quanta or photons. When a beam of light of sufficiently high energy is allowed to fall on the surface of a metal, electrons are ejected. These electrons are called photoelectrons and the phenomenon is called photoelectric effect. Threshold frequency (n0) : The minimum frequency required to eject electrons from a particular metal. Dispersion: The separation of constituent wavelengths in a definite sequence by a prism is known as dispersion. Spectrum: The series of coloured bands(wavelengths) is called spectrum. Continuous spectrum: In the spectrum of incandescent solid or of the Sun, the coloured bands are adjacent and one band merges into another. This kind of spectrum is known as Continuous spectrum. Atomic Spectra: The spectrum obtained on account of the characteristic behaviour of an individual atom is called as atomic spectrum. Absorption spectrum: The spectrum obtained by the selective absorption of certain wavelengths by a substance from the electro- magnetic radiations to which to which it is exposed is known as absorption spectrum. 8 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI Know the Formulae Velocity of wave = frequency wavelength c=nl Velocity of light = 3 1010 cm s 1 or 3 108 m/s Wave number = = 1 wavelength ( in cm ) 1 E = h n, where n is the frequency of emitted radiation and h is the Planck s constant. E = h.c. n , where n is the wave number. Einstein s photo electric emission : mv2 = h(n - n0) Balmer formula : 1 1 = 109677 2 2 n1 n2 TOPIC-3 Bohr s Atomic Model Revision Notes According to Bohr s model of atom, the electrons move around the nucleus in certain specifically permitted circular orbits called energy levels or energy states. The promotion of an electron from one energy level to another is called electronic transition. The energy state corresponding to the minimum energy is called ground state. Angular momentum of electron = mvr An electron absorbs a definite quantum of energy on excitation while an electron emits a definite quantum of energy on de-excitation. Know the Definitions The energy state corresponding to minimum energy is termed as the ground state. Zeeman effect : When a magnetic field is applied on an atom, its usually observed spectral lines get split. This effect is known as Zeeman Effect. Stark effect : When an electric field is applied on an atom, its usually observed spectral lines get split. This effect is known as stark effect. Heisenberg s Uncertainty Principle : It states that the position and velocity of an electron can never be determined simultaneously and accurately. TOPIC-4 Modern Concept of Structure of Atom Revision Notes The wave function represents the amplitude of the electron wave. The square of the wave function represents the probability of finding an electron at various places in a given region around the nucleus. Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 9 deBroglie Equation: h mv Quantum numbers specify the location of an electron in an atom. The three-dimensional region in the space around the nucleus in which the probability of finding an electron is maximum, is called an orbital 1312 Z 2 Energy of the principal shell is given by: En = kJ mol 1 n2 0.529n 2 Radius of the principal shell is given by = rn = Z Orbit is a well-defined circular path in which electrons were supposed to move in Bohr s model. Quantum numbers are defined as the numbers which designate and distinguish various atomic orbitals and electrons present in an atom. Principal quantum number (n) determines the principal shell in which the electron lies. Azimuthal quantum number (l) determines the sub-shell in which the electron lies. Magnetic quantum number (m) tells the number of orbitals which correspond to a particular subshell. Spin quantum number (s) represents spin of electron i.e. clockwise (+1/2) and anti clockwise (-1/2) The rotation of an electron around its our axis is called spin. Shapes of Orbitals = Orbital Shape s Spherical p Dumb bell Nodal planes/nodes: The region in which probability density function reduces to zero is called nodal surface. According to Pauli s exclusion principle, Two electrons in an atom can never have identical sets of four quantum numbers. The maximum number of electrons that can be accommodated in a shell is 2n2 where n is the principal quantum number of the shell. An orbital can accommodate a maximum of 2 electrons only. According to Hund s rule of maximum multiplicity, While filling different orbitals of a subshell, pairing of electrons takes place only when all the orbitals of a subshell are singly occupied. According to Aufbau principle. Electrons are filled in various orbitals in the increasing order of energies and fill up the orbitals of lower energy first. The increasing order of energies of various orbitals are : 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s ll CHAPTER-3 CLASSIFICATION OF ELEMENTS AND PERIODICITY IN PROPERTIES TOPIC-1 History of Periodic Table Revision Notes A Periodic table is an arrangement of all the known elements based on periodic law. Dobereiner suggested that elements could be arranged in groups of three called as triads such that the middle element has an atomic weight almost the average of other two. Cooke s classified the elements on the basis of homologous series of their physical and chemical properties. Newland suggested that elements are arranged in the increasing order of their atomic weights. The principal quantum number of the valence shell represents the period to which an element belongs. The subshell in which the last electron enters, represents the name of block to which the given element belongs. The number of electrons present in its outermost or penultimate (n 1) shell represents the group to which an element belongs. 10 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI The elements which belong to groups 1 and 2 are called s-block elements. The elements which belong to groups 13, 14, 15, 16, 17 and 18 are called p-block elements. The element in which the last electron enters into the d-subshell of penultimate shell [(n 1)d shell] are called transition elements or d-block elements. Transition elements have high melting and boiling points. The elements in which the last electron enters into (n 2)f subshell are called inner transition elements or f-block elements. Period Orbitals filled and their order of filling Electrons accommodated Number of elements First 1s 2 2 Second 2s, 2p 2+6 8 Third 3s, 3p 2+6 8 Fourth 4s, 3d, 4p 2+10+6 18 Fifth 5s, 4d, 5p 2+10+6 18 Sixth 6s, 5d, 4f, 5d, 6p 2+1+14+9+6 32 Seventh 7s, 6d, 5f, 6d,7p 2+1+14+9+6 32 (still incomplete) Know the Definitions According to Newland s law of octaves, If the elements were arranged in the increasing order of their atomic weights, the properties of every 8th element was similar to those of the first one According to modern periodic law, The physical and chemical properties of the elements are the periodic functions of their atomic numbers . In the periodic table, the horizontal rows are called period and vertical columns are called groups. GROUP 1, 2 GROUP 18 Representative elements N O B L E Transition elements Group 3-10 s BLOCK ns1-2 d BLOCK (n 1)d1 10ns1 or 2 p BLOCK ns2np1 6 G A S E S Inner Transition elements f BLOCK (n 2)f1 14 (n 1)d0 or 1ns2 s-Block 1 1s p-Block 2 13 14 15 16 17 2p 2s 3s d-Block 3 4 5 6 7 8 9 3p 10 11 12 4p 4s 3d 5s 4d 5p 6s 5d 6p 7s 6d 7p f-Block 4f 5f 18 1s Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 11 Know the Terms Dulong Petit s Law states that the specific heat per unit mass of a variety of solids, and divided by the atomic weights of those solids the resultant per-atom specific heat was essentially constant. Differentiating electron: It is the last electron that is added when you are building up the electronic configuration of an atom. It differentiates the atom from the one just before it in the periodic table. Eg. E.C. of Gallium is [Ar]4s23d104p1. The element before Ga in periodic table is Zn with E.C. [Ar]4s23d10. Thus, 4p1 is differentiating electron. In sodium, 3s1 is the differentiating electron. TOPIC-2 Trends in Periodic Table Revision Notes Except Helium the general configuration of noble gases is ns2 np6. The elements present in the s-block and the p-block of the periodic table are called representative elements or normal elements. The elements which belong to groups 1 and 2 are called s-block elements. The elements of group 1 are called alkali metals. The elements of group 2 are called alkaline earth metals. The elements which belong to groups 13, 14, 15, 16, 17 and 18 are called p-block elements. The elements in which the last electron enter into the d subshell of penultimate shell [(n 1) d shell] are called transition elements or d-block elements. Transition elements have high melting and boiling points. The elements in which the last electron enters into (n 2)f sub shell are called inner transition elements or f-block elements. Atomic radius is defined as the distance from the centre of the nucleus to the outermost shell of electrons. Van der Waals radius is defined as one-half of the distance between the nuclei of two atoms of the same substance at their closest approach. Atomic radii decreases across the period and increases down the group. On moving from left to right in a period, the atomic volumes of the elements first decrease and then increase. They increase on going down the group. The radius of a cation is always smaller than the radius of the atom from which it is formed, while the radius of an anion is always larger than that of the parent atom. On moving from left to right in a period, the valency with respect to hydrogen and chlorine increases from 1 to 4 and then decreases from 4 to zero. In a group, all the elements possess same number of valence electrons. Therefore, the valency remains same. The amount of energy required to remove the loosely bound electron from an isolated gaseous atom to form a gaseous ion is called ionization enthalpy of that atom. IE is expressed in the units of kJ mol 1. Ionization Potential is expressed in terms of eV. 1eV = 1.6021 10 19J = 1.6021 10 22 kJ. IE decreases with increase in size. IE increases with increase in nuclear charge provided the valence shell remains the same. IE increases with increase in atomic number across a period. For the same shell, the ionization energy follows the order s > p > d > f Electron gain enthalpy is expressed in the units of kJ mol 1. Covalent bond involves sharing of valence electrons. Two similar atoms are 100% covalent. In two dissimilar atoms, the covalent bond is partially ionic and the constituent atoms appear to have partial positive and negative charges. Electronegativity is a property of an atom to pull an electron towards its own side in a covalent bond. 12 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI Know the Definitions The elements which possess all the energy levels completely filled. i.e. they possess stable energy configuration are called noble gases. Periodicity : The periodic repetition of elements having similar properties after regular intervals of time is called periodicity. Atomic volume of an element is defined as the volume occupied by one gram atom of that element. Ionic radius of an ion is defined as the distance from its nucleus to the point up to which the nucleus has influence on the electron cloud of the ion. The ions of different elements which have the same number of electrons are known as isoelectronic ions. The combining capacity of an element is known as its valency. Valency is also defined as number of hydrogen atoms or the number of chlorine atoms or twice the number of oxygen atoms that combine with an atom of the given element. The amount of energy involved on addition of an electron to the outermost shell of an isolated gaseous atom of that element to form a gaseous anion is called electron gain enthalpy. Electronegativity of an atom may be defined as the tendency of that atom to attract the bonding electrons towards itself in a covalent bond. The tendency of an atom to attract the bonding or shared pair of electrons towards its own side in a covalent bond is called the electronegativity of that atom. The elements which have no tendency to pull electrons towards itself are called electropositive elements. Know the Formulae Pauling scale : 1/2 X A X B = 0.208 EA B EA A EB B Mulliken Scale : x= (IE) + (EA) 2 Know the Terms Bohr Bury scheme: The maximum electrons that can be present in a shell is given by the rule 2n2, where n is the orbit number or energy level. Paramagnetic: Paramagnetic electron is an unpaired electron. An atom is considered to be paramagnetic, if one orbital has net spin. Oxidation state : It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. Lattice energy : It is the measure of energy released when ions are combined to make a compound. ll CHAPTER-4 CHEMICAL BONDING AND MOLECULAR STRUCTURE TOPIC-1 Bonding and its types Revision Notes A chemical bond is an attractive force which holds various constituents (atoms, ions etc) together in different chemical species. A chemical bond is thus some sort of interatomic attraction which holds the two atoms together. Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 13 The minimum energy corresponds to maximum stability. The noble gases have completely filled valence shell. According to Kossel and Lewis, during the formation of a chemical bond, atoms combine together by gaining, losing or sharing electrons in such a way that they acquire stable noble gas configuration. The electrons present in the outer most shell of an atom is called valence electrons. Ionic bond between two atoms is the electrostatic force of attraction which holds together the ions of combining atoms formed by complete transfer of one or more electrons from electro positive to electronegative atom. The reluctance of ns2 electron pair to get excited and to take part in bond formation is called bond pair effect. The chemical bond which is formed by mutual sharing of electrons between two atoms is called covalent bond. If Hhydration > Hlattice, the salt would dissolve in water. Hhydration < Hlattice, the salt would ordinarily not dissolve in water. Know the Definitions Octet rule : During the formation of a molecule, an atom of a particular element gains, loses or shares electrons until it acquires a stable configuration of eight electrons in its valence shell. The number of electrons that an atom gain or loses during the formation of ionic bond is called electrovalency. Lattice energy : The amount of energy liberated in condensing the required number of cations and anions to form the lattice of one gram mole of an ionic compound is called lattice energy of that compound. Hydration energy: The enthalpy change involved in the hydration of one mole of gaseous ions of each type of an ionic solid is called hydration energy. TOPIC-2 Covalent Bond Revision Notes The sharing of two pairs of electrons is known as double bond and the sharing of three pair of electrons is called as triple bond. Variable covalency of an element depends on availability of unshared pair of electrons. The magnitude of bond energy depends on : Size of the atoms. Multiplicity of the bonds. The bond energy of double bond is much higher than the single bond between the same atoms. The average distance between the centres of the nuclei of two bonded atoms in a molecule is termed as the bond length. The angle between two covalent bonds in a molecule is called bond angle. The formal charge on an atom in a polyatomic molecule or ion is defined as the difference between the number of valence electrons possessed by that atom in the free state and the number of electrons assigned to that atom in the Lewis structure of the molecule or ion. Calculation of formal charge on an atom in a polyatomic molecule or ion. Formal Charge Know the Definitions The bond formed as a result of the electrostatic attraction between the positive and negative ions is called electrovalent bond or ionic bond. The attractive forces which comes into existence due to the mutual sharing of electrons between two atoms of similar electronegativity or having small differences in electro negativities is called covalent bond. Covalency: The covalency of an element in a covalent compound is equal to the number of covalent bonds formed by its one atom with other atoms of the same element or different elements. The amount of energy required to break one mole of bonds of the same kind to separate the bonded atoms in the gaseous state is called the bond energy. 14 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI Know the Formulae Formal charge on an atom Total number of Total number of valence Total number of non-bonding 1 = bonding (shared) electrons in a polyatomic molecular ion electrons the free atom (lone pair) electrons 2 Formal charge on an atom Total number of Total number of valence Total number of non-bonding 1 = bonding (shared) electrons in a polyatomic molecular ion electrons the free atom (lone pair) electrons 2 TOPIC-3 Dipole moment and Resonance Revision Notes The unit of dipole moment is Debye (D). 1 D = 1 10 18 e.s.u. cm. Higher the difference in the electronegativities of the two atoms, greater is the dipole moment of the diatomic molecule. When the difference in electro negativities is 1.7, then the bond is roughly 50% ionic. On account of polarisation of the anion, the ionic bond develops a partial covalent character. The extent of polarisation in an ionic compound is governed by certain rules called Fajan s rule. Fajan s Rules : Smaller the size of cation and greater the size of anion, greater is the extent of polarization in an ionic compound. Larger the charge on cation and anion, greater is the extent of polarization in an ionic compound. A cation with outer electronic configuration of the type s2p6d10 has a greater polarizing power than cation having the same size and same charge but having outer electronic configuration of the type s2p6. Higher the dielectric constant of the medium, lesser is the extent of polarization in an ionic compound. Coordinate covalent bond is a covalent bond in which both the electrons of the shared pair come from one of the two combining atoms. It is represented by an arrow ( ) pointing from donor to acceptor. The forces which come into existence by dipole-dipole interactions are called Keesom forces. The forces developed due to interaction between a dipole and an induced dipole are called Debye forces. Debye forces are not affected by temperature. They depend upon the distance between dipole and induced dipole. The forces developed due to interaction between temporary dipole and induced dipole are called London forces. The shared electron pair existing between the two covalently bonded atom is called bond pair. The valence shell electron pairs of bonded atom not taking part in bond formation, is known as lone pair of electrons. According to VSEPR theory, lp lp > lp bp > bp bp Where lp = lone pair of electrons, bp = bond pair of electrons. Know the Definitions Dipole moment is defined as the product of the magnitude of the charge present on either of the two atoms and the distance by which the two atoms are separated in the molecule. When two oppositely charged ions approach each other closely, the positively charged cation attracts the outermost electrons of the anion and repel its nucleus. This causes a distortion of the anion and its electron density gets drifted towards the cation resulting in some sharing of electrons between the two. This phenomenon is called polarization. When hydrogen bonding exists within the same molecule, it is termed as intramolecular hydrogen bonding. When hydrogen bonding exists between two molecules of the same or different substances, it is termed as Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 15 intermolecular hydrogen bonding. The weak electrostatic attractive forces which exist between all kinds of atoms, molecules and ions when they are brought sufficiently close to each other are called van der Waals forces. Know the Formulae = q r where = Dipole moment, q = magnitude of the charge and r = distance between two atoms TOPIC-4 Quantum Theory of covalent bond and hybridization Revision Notes When two atomic orbitals come closer and overlap, the maximum electron density lies in the region of overlap. An axial overlap between the two orbitals of same energy content always form a stronger bond. Overlapping of two atomic orbitals from a new orbital known as molecular orbital. The bonding molecular orbital is a low energy orbital. The antibonding molecular orbital is a repulsive orbital of higher energy. The probability of finding the electrons between the nuclei is almost zero. The order of energies of molecular orbitals is calculated on the basis of ultra violet spectroscopy. The sequence of energy for homonuclear diatomic molecule is : (except O2 and F2 molecules) s1s < s*1s < s2s < s*2s < [p2px p2py] < s2pz < [p*2px p*2py] < s*2pz Hybridization means mixing of orbitals. Know the Definitions Bond order may be defined as one half of the difference between number of electrons in bonding molecular orbitals and number of electrons in anti -bonding molecular orbitals. Hybridization may be defined as phenomenon of intermixing of atomic orbitals of comparable energies to form a set of same number of new orbitals of equal energy and identical in all respect. Know the Formulae Bond order = 1 No. of electrons in bonding No. of eleectrons in antibonding molecular orbitals molecular orbitals 2 1 [ Nb N a ] 2 = Know the Terms (a) Interstitial compounds : They are chemically inert compounds with high melting point as compared to pure metals. (b) Diamagnetic compounds : When all the electrons in a molecule are paired, the substance is diamagnetic. (c) Paramagnetic : When one or more electrons in a molecule are unpaired, it is paramagnetic. (d) Coalescence : Joining or merging of elements to form one mass or whole. (e) Aufbau principle : It explains that in the ground state of an atom or ion, electrons fill atomic orbital of lowest the available energy levels before occupying higher energy levels. ll 16 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI CHAPTER-5 STATES OF MATTER - GASES AND LIQUIDS TOPIC-1 Introduction and gas Laws Revision Notes Matter exists in three forms viz solid, liquid and gas. In solids, the constituent particles are orderly packed and occupy fixed positions in the lattice. In liquids, the constituent particles are less orderly packed. In gases, there is no definite arrangement of constituent particles and they are widely separated from one another. The existence of matter in a particular state depends upon the conditions of temperature and pressure. Van der Waals forces are the intermolecular forces which arise due to dipole dipole interactions, dipole induced dipole interactions and dispersion forces. The forces which come into existence due to dipole -dipole interactions are called as Keesom forces. The forces developed due to interaction between a dipole and an induced dipole is called as Debye forces. Hydrogen bonding is due to dipole -dipole interaction between the molecules. Thermal energy arises in a body due to motion of its atoms and molecules. The volume of a gas is defined as the space in which its molecule can move freely under a particular set of conditions. The forces exerted by the gas per unit area of the walls of the containing vessel is called pressure of the gas. A standard pressure of 1 atm may be defined as the pressure exerted by exactly 76 cm of Hg at 0 C 1 atm = 76cm Hg = 760 mm Hg = 101.325 103 Nm 2 = 101.325 103 Pa = 101.325 kPa 1 bar = 0.987 atm The volume of a gas decreases by t Vt = V0 1 + 273 1 of its volume at 0 C for each 1 C fall in temperature. 273 The lowest possible temperature ( 273 C) at which all gases are supposed to occupy zero volume is called absolute zero of temperature. A scale of temperature based on absolute zero is called absolute scale of temperature or Kelvin scale of temperature. 273.15 C = 0 K One mole of gas contains 6.023 1023 molecules. Temperature on Kelvin scale (K) = temp on Celsius scale ( C) + 273.15 Under STP conditions, 1 mole of any gas occupies a volume of 22.4 litres. This volume is referred to as molar volume. Ideal Gas Equation PV = nRT where P = Pressure V = Volume n = Number of moles of the gas R = Gas constant (8.314 JK 1 mol 1) T = Absolute temperature 22.4L of any gas at STP contains 6.022 1023 molecules. 1 mole of gas contains 6.022 1023 molecules. V number of molecules (at constant temperature and pressure) V number of moles (at constant temperature and pressure) Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 17 Know the Definitions Intermolecular forces: The forces existing between the molecules of a substance are called as intermolecular forces, while those existing within each molecule of a substance are referred to as intra molecular forces. Hydrogen bonding: When the positively charged hydrogen atom of one molecule may attract the negatively charged atom of some other molecule, and the two molecules can be linked together through a weak force of attraction. This weak force of attraction, is called as hydrogen bonding. Boyle s law: The volume of a given mass of a gas is inversely proportional to its pressure at constant temperature . V P (where V = volume, P = Pressure) Charle s law: The volume of a given mass of a gas is directly proportional to its absolute temperature at constant pressure . V T (where V = volume, T = absolute temperature) Pressure Temperature Law (Gay Lussac s Law) : The pressure of a given mass of a gas is directly proportional to its absolute temperature at constant volume . P T Avogadro s law: Equal volumes of all gases contain equal number of molecules under similar conditions of temperature and pressure . Gay Lussac s law: At constant volume, the pressure of a given mass of a gas increases or decreases by pressure at 0 C for every 1 C rise or fall in temperature. Know the Formulae K = C + 273.15 Boyle s Law : P1V1 = P2V2 Charle s Law : V1 V2 = T1 T2 t Vt = V0 1 + 273 Gay Lussac s Law : m M n = no. of moles. P1 T1 = P2 T2 n = M is the gram molecular mass of the gas m = mass of the gas in grams Ideal gas equation: P1V1 P2V2 = T T2 1 PV = constant = k T k a n k =nR R is a constant of proportionality, known as Universal gas constant. PV = nR T PV = nRT ..Ideal Gas Equation 1 of its 273 18 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI TOPIC-2 Dalton s Partial pressure and Kinetic Molecular theory Revision Notes According to Dalton s Law, P = P1 + P2 + P3 + (at constant T and V) of water vapour is constant at a particular temperature and is known as aqueous tension at that temperature. The rate of effusion is inversely proportional to the square root of its density at constant temperature and pressure. The gases show deviation in behaviour when precise measurements are carried out at high pressure or low temperature. The gas which obeys the gas laws and the gas equation PV =nRT under all set of conditions of temperature and pressure is said to be an ideal gas. The gases which do not obey gas laws and do not follow ideal gas equation are called as real gases/non-ideal gases. At absolute zero, the total kinetic energy of one mole of a gas as well as the average kinetic energy of one molecule of the gas reduces to zero. 2 kT (constant) 3 The most portable velocity is defined as the velocity possessed by the largest friction of molecules at a particular temperature corresponding to the highest peak on the velocity distribution curve. Root mean square velocity of a molecule becomes zero at absolute zero. The most portable velocity is defined as the velocity possessed by the largest friction of molecules at a particular temperature corresponding to the highest peak on the velocity distribution curve. PV = Know the Definitions According to Dalton s law of partial pressure, the total pressure exerted by a mixture of two or more non-reacting gases enclosed in a definite volume is equal to the sum of individual partial pressures of the gases present in the mixture at constant temperature . According to Graham s law of diffusion, The rate of diffusion of a gas is inversely proportional to the square root of its density at constant temperature and pressure . The spontaneous intermixing of two or more gases even against gravity is known as diffusion. The phenomenon by which a gas is allowed to escape through a fine orifice is called effusion. The deviation of real gas from ideal gas behaviour can be expressed in terms of compressibility factor (Z). PV nRT For an ideal gas Z = 1 For a real gas Z > 1 (Positive deviation) or Z < 1 (Negative deviation) Z = Know the Formulae Different formulae used in diffusion: M=2 d r1 = r2 r= d2 = d1 M2 M1 d2 = d1 M2 M1 V t V1 = V2 where, V is the volume of gas diffused. Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 19 M is the molecular mass r is the rate of diffusion d is the densities For one mole of gas. 1 PV = m Nu2 3 where, N = Avogadro s number 6.023 1023 molecules. Total KE of one mole of gas at absolute temperature, T : 3 EK = RT 2 3 E K = kT 2 R where k = , known as Boltzmann s constant N Boltzmann s constant = 1.3807 10 23 JK 1 Expression for average velocity: 8 RT u= M where M is the molecular mass u= 3RT M 2RT = M Compressibility factor: PV Z= nRT For an ideal gas Z = 1 For a real gas Z > 1 (Positive deviation) or Z < 1 (Negative deviation) TOPIC-3 Liquefaction of Gases Revision Notes Critical pressure of a gas is the pressure required to liquify the gas at critical temperature. Critical volume of the gas is the volume occupied by one mole of a gas at its critical temperature and critical pressure. Vc = 3b (Vc = Critical volume) The amount of heat required to evaporate the given liquid at a particular temperature is called heat of vaporization of that liquid. Boiling point of the liquid is defined as the temperature at which the vapour pressure of that liquid becomes equal to the atmospheric pressure. The force acting perpendicular to any line of unit length drown on the surface of a liquid is called the surface tension of that liquid. The forces of attraction acting between the molecules of the same type are known as cohesive forces. The forces of attraction acting between the molecules of different types are known as adhesive forces. Know the Definitions Critical temperature of a gas is that temperature above which it is not possible to liquefy that gas by applying any amount of pressure. Joule Thomson effect: When a highly compressed gas, is passed through a porous plug from high pressure to low pressure region under adiabatic conditions at a temperature below its inversion temperature, it causes decrease in temperature. This effect is called as Joule-Thomson s effect and is applied for the liquefaction of gases. 20 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI The pressure exerted by the vapour of a liquid at a particular temperature in a state of dynamic equilibrium is called the vapour pressure of that liquid at that temperature. Viscosity is defined as a property of liquid which determines the rate of flow. Know the Formulae 8a (Tc = Critical temperature) 27 bR a Pc = 27 b 2 where, Pc = Critical pressure SI unit of Surface tension : Jm 2 or Nm 1 CGS unit : dynes cm 1 Tc = Know the Terms Diffusion: The intermingling of substances by the natural movement of their particles. Density : It is mass per unit volume. Cohesive force: It is the intermolecular attractive force acting between two similar substances when in contact. Adhesive force: It is the intermolecular attractive force acting between two dissimilar substances when in contact. ll CHAPTER-6 CHEMICAL THERMODYNAMICS TOPIC-1 First law of thermodynamics Revision Notes Chemical thermodynamics deals with the energy changes involved in chemical transformations. It deals with the study of different forms of energy involved in chemical reactions and the quantitative relationship between them particularly for chemical systems. The chemical reaction which involves evolution of heat is called exothermic reaction. The chemical reaction which involves absorption of heat is called endothermic reaction. A thermodynamic system is a quantity of matter of fixed identity, around which we can draw a boundary. The boundaries may be real or imaginary. Everything outside the boundary is surroundings. Work = applied force displacement of the point of application Work done against gravity = intensity factor x capacity factor = mgh (joules) Pressure volume work = P V Electrical work = EMF quantity of electricity = nEF Work done on the system = +w Work done by the system = w U Molar heat capacity is given by : Cv = T v First law: It deals with the conservation of energy. Second Law: It prevents the transfer of heat from a body at lower temperature to a body at higher temperature without the involvement of external energy in some form. Third law: It stresses on the fact that the molecule in a system becomes perfectly motionless at absolute zero resulting in zero entropy of the system. Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 21 Know the Definitions The branch of science which deals with the energy changes associated with chemical reactions is called chemical thermodynamics. Heat : The form of energy exchanged between a system and the surroundings when the two are at different temperatures is commonly known as heat. Work : The term work usually refers to mechanical work which is said to have been done if the point of application of a force is displaced in the direction of the force. According to first law of thermodynamics, Energy can neither be created nor be destroyed although it can be converted from one form to another. Internal Energy: The total amount of energy associated with a fixed amount of a substance under a given set of conditions is referred to as the internal energy or intrinsic energy of that system. Molar heat capacity at constant volume is defined as amount of heat required to raise the temperature of one mole of a gas by 1K at constant volume. Enthalpy: The sum of internal energy and pressure -volume energy of a system, under a particular set of conditions is referred to as enthalpy of the system. Mathematically, H = U + PV, where U is the internal energy of the system, P represents pressure and V represents volume of the system. Enthalpy of the system is defined as the sum of internal energy and P V energy of a system under a particular set of condition. H = E + PV The temperature, below which cooling and above which heating is observed when a gas is passed through a porous plug from high pressure to low pressure region under adiabatic conditions is called inversion temperature of that gas. Joule Thomson coefficient is defined as the rate of change of temperature with respect to the pressure at constant enthalpy during the Joule Thomson expression. It is represented by = 0 for real gas. This implies real gas suffers neither heating nor cooling during Joule - Thomson expansion. Know the Terms Thermodynamics: The branch of physical science that deals with the relations between heat and other forms of energy. Isothermal process : Isothermal process is a change of a system, in which the temperature remains constant. TOPIC-2 Heat Capacity and Second Law of Thermodynamics Revision Notes Heat capacity is represented by C. The specific heat capacity of a system is the amount of heat required to raise the temperature of unit mass of the substance by 1 C (or 1 K). It is represented by c. The molar heat capacity of a system is defined as the amount of heat required to raise the temperature of one mole if the substance by 1 K. It is represented by Cm CGS unit = cal K 1 mol 1 SI units = JK 1 mol 1 A process which proceeds of its own accord under given set of conditions, without any outside assistance, is called a spontaneous process. All spontaneous processes are thermodynamically irreversible. The increase in entropy means an increase in the disorder or a decrease in the ordered energy which is available for useful work. 22 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI This state of affairs will totally paralyse our activities and life will come to a standstill. Such a state of affair will be thermal death of the inhabitants of universe. The process which can proceed neither by themselves nor by initiation are called as non -spontaneous process. The tendency of a process to occur spontaneously is called spontaneity. Know the Definitions Heat capacity of the system is defined as the amount of heat required to increase the temperature of the system by 1 C (or 1 K). The specific heat capacity of a system is the amount of heat required to raise the temperature of unit mass of the substance by 1 C (or 1 K). The amount of energy required to raise the temperature of one mole of a gas by 1 K at constant volume is called heat capacity at constant volume. The amount of energy required to raise the temperature of one mole of a gas by 1 K at constant pressure is called heat capacity at constant pressure. The molar heat capacity of a system is defined as the amount of heat required to raise the temperature of one mole if the substance by 1 K. The tendency of a process to occur simultaneously is called spontaneity. TOPIC-3 Third law Thermodynamics and Hess's Law Revision Notes The calorific value of a fuel is defined as the amount of heat produced when one gram of the substance is completely burnt in presence of air. The value of H at 298 K and one atmospheric pressure is called standard enthalpy of the reaction and is denoted by rH . The enthalpy change involved in the complete neutralization of one gram equivalent of acid by one gram equivalent of base or vice-versa in dilute solution is called heat of neutralization. Heat of solution or entropy of solution is defined as the change in enthalpy of the system when one mole of a substance is dissolved in large excess of a solvent so that further dissolution does not produce any change in enthalpy. The enthalpy change involved in the transition of one mole of element from one allotropic form into another is called heat of transition. According to Hess s law of constant heat summation, The enthalpy change in a chemical reaction is the same whether the reaction occurs in one step or several steps. If it occurs in several steps, the enthalpy of the reaction is algebraic sum of the enthalpies of reaction corresponding to all the steps . r G = 2.303 RT log10K where rG = Change in free energy of reaction R = Gas constant T = Absolute temperature K = Equilibrium constant rG = nFEo where n = number of moles of electrons gain or loss F = 1 Faraday (96500 C) Eo = Standard electrode potential Know the Definitions The enthalpy change during a chemical reaction when the number of moles of reactants is completely change in to the products is called heat of reaction. Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 23 The enthalpy change involved in the complete combustion of one mole of the substance in the presence of air is called heat of combustion. The enthalpy change involved in conversion of one mole of a solid substance into the liquid state at its melting point is called heat of fusion. The heat of vaporization or enthalpy of vaporization is defined as the change in enthalpy of the system when one of a liquid change into vapour or gaseous state at its boiling point. The heat of sublimation or enthalpy of sublimation is defined as the change in enthalpy of the system when one mole of a solid is directly converted into gaseous state at a temperature below its melting point. Know the Terms Allotropy: When an element can exist in more than one form. They are the structural modifications of an element. Fuel: The materials like coal, gas that burns to produce energy. Arrhenius theory: The theory suggests an acid is a substance that dissociate in water to yield H+ ions and bases ionize in water to yield OH ions. ll CHAPTER-7 EQUILIBRIUM TOPIC-1 Equilibrium Revision Notes The state at which the concentrations of all reactants and products become constant is called state of equilibrium. The state of equilibrium is represented by . The state of equilibrium is not only attained in chemical processes, but also in physical processes. The state of equilibrium helps us to know how far a reaction has proceeded. When a solid is taken at its melting point, both solid and liquid phase exist in equilibrium. The stage of the system at which the rates of the forward and backward reactions become equal is called dynamic equilibrium. The mixture of reactants and products in the equilibrium state is called an equilibrium mixture. The equilibrium which involves physical process is called physical equilibrium. The pressure at which the liquid and vapour phases exist together in equilibrium is called vapour pressure of the liquid at the given temperature. A solution in which no more solute can be dissolved at a particular temperature is called saturated solution. Henry s law is applicable to ideal gases only. The state of equilibrium involving a chemical system is referred to as chemical equilibrium. For solid liquid equilibrium, there is only one temperature (melting point) at 1 atm (1.013 bar) at which the phases can coexist. For solid vapour equilibrium, the vapour pressure is constant at a given temperature. For dissolution of solids in liquids, the solubility is constant at a temperature. For dissolution of gases in liquids, the concentration of a gas in liquid is proportional to the pressure (concentration) of the gas over the liquid. The state of equilibrium involving a chemical system is called equilibrium. The solubility of gas in a liquid, depends on pressure. When active mass are expressed in terms of partial pressure, the equilibrium constant K is written as Kp. In practice, Kc is generally written as K only. While Kp is always written as Kp. Equilibrium constant for the backward section is the inverse of the equilibrium constant for the reaction in the forward direction. 24 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI The ratio of product of concentrations of the products to those of the reactants with each concentration term raised to the power equal to the stoichiometric coefficient is called reaction quotient (Q) or concentration quotient. The equilibrium constant for a particular reaction is constant at a particular temperature. The equilibrium constant does not depend upon the initial concentration of reactants. The larger the value of equilibrium constant (K), greater is the extent to which reactants are converted into the products. Prediction of direction of reaction If Q < K, reaction does not go from left to right. If Q > K, reaction does not go from right to left. If Q = K, no net reaction occurs. Where Q = Reaction Quotient; K = Equilibrium Constant Know the Definitions Normal melting point or normal freezing point : For any pure substance the temperature at which the solid and liquid phase are at equilibrium at one atmospheric pressure is called the normal melting point or normal freezing point of the substance. A solution in which no more solute can be dissolved at a particular temperature is called the saturated solution at that temperature. The amount of solute required to prepare a saturated solution in a given quantity of solvent is called the solubility of solute at that temperature. Dissolution: When a solid is added to a liquid, the molecular vibrations tend the molecules to pass into the liquid phase. This, tendency is called dissolution. Precipitation: As the concentration of molecules into the liquid phases increases, they start returning back into the solid phase. This tendency is called precipitation. Henry s Law: The mass of a gas dissolved in a given mass of a solvent at a constant temperature is proportional to the pressure of the gas at equilibrium with the solution provided the gas does not undergo any chemical change during the formation of the solution . The chemical reaction which proceeds mainly in one direction is called irreversible reaction. The chemical reaction which proceeds simultaneously in both the directions is called reversible reaction. Law of chemical equilibrium: At a given temperature, the product of concentration of the reaction products raised to the respective stoichiometric coefficient in the balanced chemical equation divided by the product of concentration of the reactants raised to their individual stoichiometric coefficients has a constant value. Know the Terms A system in which there is no exchange of matter with the surroundings, is called a closed system. A system in which exchange of both matter and heat occurs with the surroundings is called an open system. Manometer : A device used to measure gas pressure. TOPIC-2 Law of Chemical Equilibrium and Le Chatelier s Principle Revision Notes The value of K (equilibrium constant) for a reaction does not depend on the rate of the reaction. However, it is directly related to the thermodynamics of the reaction i.e. change in Gibbs free energy ( G). If G- ve, = the reaction is spontaneous and takes place in the forward direction. If G +ve, = + the reaction is non spontaneous. If G , = the reaction has achieved equilibrium, is the standard Gibbs free energy. The presence of catalyst help in attainment of equilibrium faster. Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 25 Know the Definitions Degree of dissociation: Degree of dissociation may be defined as the fraction of total number of moles which undergoes dissociation. Le Chatelier s Principle: When a chemical system at equilibrium is subjected to a change in concentration, pressure or temperature, the equilibrium shifts in the direction that counteracts the change. Know the Formulae = Number of moles undergoing dissociation Total number of mo oles degree of dissociation (a) = percentage dissociation 100 G = G + RT lnQ Know the Terms Stoichiometric: relating or denoting quantities of reactants in simple integral ratios Aqueous: containing water Dissociation: action of separation TOPIC-3 Ionic Equilibrium Revision Notes There are several substances which dissolve in water but do not ionise in the solution. Such substances are called non-electrolytes. An acid is a substance which dissolves to give H+ ions in aqueous solution. A base is a substance which dissociates to give OH ions in aqueous solution. According to Bronsted Lowry concept, Acids = Proton donors Bases = Proton acceptors The conjugate acid differs from its conjugate base by the proton and vice-versa. The strength of an acid is determined by its tendency to lose proton. The strength of a base is determined by its tendency to gain proton. The conjugate of a strong acid is always a weak base and the conjugate of a weak acid is always a strong base. The value of Kw remains unchanged so long as the temperature remains unchanged. The strength of an acid is determined by its tendency to lose protons. The strength of an acid may be defined as the concentration of H3O+ ions (i.e., H+ ions) in its aqueous solution at a particular temperature. An acid with a higher value of K a is a stronger acid. Higher the value of Kb, greater is the strength of a base. According to Lewis concept, Acid = Electron pair acceptor Base = Electron pair donor The pH value of a solution may be defined as the negative logarithm (base 10) of the [H3O+] concentration expressed in moles per litre. The ability of a buffer solution to resist any change in pH on addition of acid or base is called buffer action. 26 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI Know the Definitions Electrolytic solution : The solutions which allow the passage of current through them, is known as electrolytic solution. Ionic equilibrium : In an electrolytic solution, there exists an equilibrium between the ions and undissociated molecules of the substance forming the solution. This equilibrium is known as ionic equilibrium. Electrolytes : The substances which dissociate into ions in aqueous solutions are known as electrolytes. Strong electrolyte : The electrolytes which are completely ionised in solutions are called as strong electrolyte. Weak electrolyte : The electrolytes which do not dissociate much in solutions are called as weak electrolyte. Ostwald s dilution law : The degree of dissociation of a weak electrolyte is directly proportional to the square root of its dilution. Buffer solution : A buffer solution is the solution which resists the change in pH on addition of small amount of acid or base. Know the Formulae pOH = log10[OH] pH + pOH = 14 pH + pOH = Kw Kw = [H3O+] [OH ], where Kw is the ionic product of water. Know the Terms Cations : Positive ions Anions : negative ions Polyprotic acid : An acid that can denote more than one proton or hydrogen atom per molecule to an aqueous solution. TOPIC-4 Solubility Product Revision Notes A salt of type AB is called as binary salt. For binary salt, the solubility product is equal to the square of its solubility at a particular temperature. A salt of type, AB2 or A2B are called ternary salts. For a ternary salt, the solubility product is four times the cube of the solubility of the salt at a given temperature. Kh = Kw Kb The degree of hydrolysis of salt is the fraction of total number of moles which undergo hydrolysis when equilibrium is attained. Know the Definitions Solubility product : The solubility product of sparingly soluble salt at a given temperature is the product of the concentration of ions in the saturated solution, with each concentration term raised to the power equal to the stoichiometric coefficient of the corresponding ion. Acid base indicator : The organic compound which indicates the end point of an acid base titration by a visual change in its colour is called an acid-base indicator. Salt hydrolysis : The phenomenon involving the interaction of cations or anions (or both) of a salt with H+ or OH ions of water leading to the formation of an acidic or alkaline or sometimes even neutral solution is called as salt hydrolysis. Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 27 Know the Formulae S = K sp sp = s2 for binary salts Ksp = 4s3 for ternary salts K Kh = w K a Kb Kw h= K a Kb pH = log10[H3O+] pH = ( log10Kw) + ( log10K a) ( log10Kb) h= No. of moles of the salt undergoing hydrolysis Total no. of moles of the salt dissolved Kw h= Kb .c To calculate pH of a solution of salt of strong acid and a weak base. pH = pKw pKb log10c ll CHAPTER-8 REDOX REACTIONS Revision Notes The reactions which involve both oxidation and reduction are called redox reactions. The oxidation number of an atom is the charge that atom would have if the compound was composed of ions. Oxidizing agent undergoes decrease in the oxidation number of one or more of its elements. Reducing agent undergoes increase in the oxidation number of one or more of its elements. The combination reaction is the chemical combination or two elements of the same or different type. The decomposition reaction is one which involves breakdown of a compound into two or more compounds. The reaction which involves the replacement of ion or an atom in a compound by the ion or atom of some other element is called displacement reaction. The disproportionation reaction in that reaction in which an element in one oxidation state in simultaneously oxidized and reduced. In a galvanic cell, anode is negative and cathode is positive. In a galvanic cell, the electrons flow from anode to cathode and the current flows from cathode to anode. The commonly used inert electrolytes in salt bridge are KCl, KNO3, NH4 NO3 etc. Redox reaction can be balanced by using ion electron method or oxidation number method. Titration is a technique in which the strength of a unknown solution is determined with the help of some other solution of known strength. Know the Definitions Oxidation is a process in which a substance : Adds oxygen or electronegative element. Removes hydrogen or electropositive element. Oxidation involves loss of electrons. 28 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI Reduction is a process in which a substance : Adds hydrogen or electropositive element. Removes oxygen or electronegative element. Reduction involves gain of electrons. A substance which provides oxygen or removes hydrogen is called an oxidizing agent. A substance which provides hydrogen or removes oxygen is called a reducing agent. A device which converts chemical energy into electric energy is called galvanic cell. Oxidation is the process in which a substance undergoes an increase in oxidation number. Reduction is the process in which a substance undergoes decrease in oxidation number. The titration which involve redox reactions are called redox titration. The electrode at which the process of oxidation takes place is called anode. The electrode at which the process of reduction takes place is called cathode. Know the Terms Electrochemical series : It is a series of chemical elements arranged in order of their standard electrode potential. Electronegative atoms : The ability of an atom to attract shared electrons towards itself in a covalent bond. ll CHAPTER-9 HYDROGEN TOPIC-1 Hydrogen Revision Notes Hydrogen is the most abundant element in the universe (70% of the total mass of the universe). Hydrogen atom cannot exist in free state and combine to form diatomic molecule (H2). Hydrogen was prepared by Henry Cavendish in 1766. Hydrogen is the lightest element and the first member of the periodic table. Electronic configuration of Hydrogen = 1s1 Hydrogen atom cannot exist in free state and combine together to form a diatomic molecule i.e., dihydrogen (H2). Hydrogen shows isotopes: protium, deuterium, tritium Isotopes of Hydrogen: 1 2 3 1H 1H 1H ( Protium )( Deuterium ) ( Tritium ) Very active metals like Na, K etc. decompose water at room temperature to liberate dihydrogen, 2Na + H2O 2NaOH + H2 Iron reacts with steam to produce dihydrogen by Lane s process. high temperature 3Fe + 4H 2O Fe3O4 + 4 H 2 (steam) Reaction of steam on hydrocarbon or coke at high temperature in the presence of catalyst yields hydrogen. Since the mixture of CO and H2 is used for the synthesis of methanol and a number of hydrocarbon. It is also called synthesis gas or syngas . The process producing syngas from coal is called coal gasification Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 29 The production of dihydrogen can be increased by reacting carbon monoxide of syngas mixtures with steam in the presence of iron chromate as catalyst. 673 K catalyst CO(g) + H 2O(g) CO2 (g) + H 2 (g) This reaction is called water gas shift reaction. Tritium is radioactive and emits low energy b-particles (t1/2 = 12.33 years). Laboratory preparation of Dihydrogen : Zn(s) + H2SO4(aq) ZnSO4(aq) + H2(g) Dihydrogen has two nuclear spin isomers called ortho and para dihydrogen. When the spins of the nuclei (protons) are parallel i.e. in the same direction, the dihydrogen is called ortho dihydrogen. When the spins of the nuclei are antiparallel i.e. in the opposite direction, the dihydrogen is called para dihydrogen. Hydrogenation of vegetable oil : 473 K Ni vegetable oil + H 2 solid fat Dihydrogen is used in oxy-hydrogen torch for welding. Dihydrogen is used in atomic hydrogen torch which produces temperature of the order of 4000 C and is used for welding. The hydrides of boron are called boranes. The hydrides of silicon are called silanes. The hydrides which have too few electrons for writing their conventional Lewis structures are called electrondeficient hydrides. The hydrides of the elements of group 13 are such hydrides. eg. Diborane (B2H6). The hydrides which have the required number of electrons to write their conventional Lewis structures are called electron precise hydrides. The hydrides formed by all the group 14 elements are such hydrides. eg. CH4. The hydrides which possess excess electrons present as lone pairs are called electron-rich hydrides. Such hydrides are formed by the elements of groups 15, 16 and 17. Metallic or non-stoichiometric hydrides are formed by transition elements and rare earth metals. However the metals of groups 7,8,and 9 do not form hydrides. Know the Definitions The difference in the physical properties and in the rate of reactions of isotopes of isotopes due to a difference in mass numbers is referred to as isotopic effect When the spin of the nuclei (proton) are parallel, the dihydrogen is called ortho-dihydrogen When the spin of the nuclei are anti parallel, the dihydrogen is referred to as para-dihydrogen. Know the Terms Electropositive character : The property of elements to lose electrons to form positive ions. Oxidation state : A number assigned to an element in a chemical combination. This number represents the number of electrons an atom can gain, lose or share when chemically bond with another element. Electrolysis : Chemical decomposition produced due to passing an electric current through a liquid or solution containing ions. TOPIC-2 Water Revision Notes The fresh water contributes to 2.7% of total global supply. Water is an oxide of hydrogen and consists of one part of hydrogen and eight parts of oxygen by weight and its molecular formula is H2O. 30 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI As per VSEPR theory, water possess tetrahedral shape. The density of ice is less than water and it floats on water. Water behaves as an acid, as a base, as an oxidising agent, as a reducing agent and as a ligand to metal ions. Water reacts with certain metal salts to form compounds known as hydrates. Water can be classified as hard and soft water. Hard water can also be defined as the water which contains bicarbonates, chlorides or sulphates of calcium or magnesium. Eg. sea water, water of some rivers, lakes, etc. Heavy water is the oxide of deuterium. D2O reacts slightly less slowly than H2O. Heavy water retards the growth of plants. Know the Definitions Soft water: Water which produces lather with soap solution readily is called soft water. Eg. Distilled water, rain water, etc. Hard water: Water which does not produce lather with soap solution readily is called hard water. The water which is neither acidic nor basic and is free from cations and anions that were present in hard water is called as deionised or demineralised water. Know the Terms Ligand: An ion or a molecule attached to a metal atom by coordinate bonding. TOPIC-3 Hydrogen Peroxide Revision Notes Hydrogen peroxide was discovered by L.J.Thenard. It was called as oxygenated water. Hydrogen peroxide (H2O2) has a higher density (1.44 g cm 3) than water. The process of concentration of hydrogen peroxide is a dangerous operation because the impurities catalyse its explosive dissociation. Pure H2O2 is not very stable. It decomposes into oxygen and water on standing or on heating. H2O2 oxidizes coloured vegetable and organic materials into colourless materials and so it acts as a bleaching agent. Coloured material + O colourless As hydrogen peroxide oxidises lead sulphide to lead sulphate, it is used for restoring the colour of lead paintings. 10 volume hydrogen peroxide refers to that solution of H2O2 whose 1 litre will give 10 litres of oxygen (at S.T.P) on heating. The liquid hydrogen has been used as a fuel for rockets. Hydrogen economy refers to transportation and storage of energy in the form of liquid or gaseous hydrogen. For mass basis, dihydrogen releases more energy (2.7 times) than petrol. If the problem of safe storage and high cost of production of production of hydrogen is solved, it would prove an ideal fuel not only for rockets but also for vehicles and domestic uses. Know the Definitions Hydrogen economy : Hydrogen economy refers to the transportation and storage of energy in the form of liquid or gaseous hydrogen. Know the Terms Hydrated: combining chemically with water molecules. Electrolysis: chemical decomposition due to passing of an electrolyte. ll [ 31 Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI CHAPTER-10 s-BLOCK ELEMENT TOPIC-1 Alkali metals Revision Notes The elements which belong to group 1 and group 2 are called s-block elements. The elements of group 1 are called alkali metals. The elements of group 2 are called alkaline earth metals. The general electronic configuration of s-block elements is ns1 2. The s-block elements have either 1 or 2 valence electrons. In s-block, the first element of a group (belonging to the second period) shows resemblance to the second element of the neighbouring element placed diagonally opposite to it and this type of resemblance is called diagonal relationship. Group 1 Group 2 Group 3 B Be Li Na Mg Al The reasons for diagonal relationship are: (i) Similarity in ionic sizes; (ii) Similarity in the values of electronegativities; (iii) Similarity in polarizing power. Group 1 Elements : Li, Na, K, Rb, Cs and Fr Francium is radioactive in nature. The ionic radii of alkali mental ions are smaller as compared to the atomic radii of the corresponding atoms. The density of alkali metals increases from Li to Cs. The alkali metal cations have no unpaired electrons. So, they are colourless and diamagnetic in nature. The energy involved in hydration of alkali metal ions is called hydration energy which decreases in moving from Li+ to Cs+. Alkali metals form ionic compounds. Alkali metals and their salts show characteristic colours when heated in a non-luminous flame. It is due to the fact that when an alkali metal or its salt is heated in a flame, its electrons get excited to higher energy level due to absorption of energy. When the excited electrons return back to ground state, the energy is emitted, which corresponds to the visible region so a characteristic colour is imparted to the flame. Li Na K Rb Cs Crimson Golden Pale Violet Violet Yellow violet Alkali metals are the reactive elements. It is due to their low ionisation energies and low heat of atomization. Reaction of alkali metals with oxygen : 4Li + O2 2LiO2 (Lithium monoxide) 2Na + O2 Na2O2 (Sodium peroxide) M + O2 MO2 (Superoxide) where, M = K, Rb, Cs Higher the charge on cation and anion, greater is the extent of polarisation. e.g. Al3+ > Mg2+ > Na+ Alkali metals act as strong reducing agents due to low ionisation energies. The reducing nature of alkali metals decreases in moving from Li to Cs. Among alkali metal cations, Li+ undergoes hydration to the maximum extent due to its smallest size. All alkali metals dissolve in liquid ammonia to form deep blue coloured solutions which are highly conducting. M + (x + y) NH3 M+(NH3)x + e (NH3)y ammoniated cation ammoniated electron The blue colour of the solution is due to the formation of ammoniated electrons which get excited on absorption of energy from visible light. Lithium is the only alkali metal which reacts with nitrogen to from lithium nitride (Li3N). Other alkali metals do not react with nitrogen. Due to small size of lithium, Li+ has a high positive charge density and possesses high polarizing power. It results in the formation of partial covalent nature in its compounds. 32 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI Know the Definitions The process of hydration is exothermic and the energy involved is called hydration energy. The distortion of the electron cloud of an anion by a cation is called polarisation. Know the Terms Periodicity : It refers to repetition of trends in elements properties with increasing atomic number at regular interval. Differentiating electron: the last electron that is added when we are building up the electronic configuration of an atom. Screening effect: The phenomenon which occurs when the nucleus reduces its force of attraction on the valence electrons due to the presence of electrons in the inner shell. TOPIC-2 Some important compounds of sodium Revision Notes Sea water is the main source of sodium chloride. Sodium chloride also known as common salt is an essential constituent of food. Sodium carbonate, also known as soda ash or washing soda is prepared by Solvay process or Ammonia soda process. In the presence of excess carbon dioxide, sodium carbonate is sparingly soluble in water. Know the Definitions A phenomenon of the emission of electrons from the surface of the metal on irradiating the metal surface with electromagnetic radiation is called photoelectric effect and the electrons thus ejected are called photoelectrons. Know the Terms Polarising power : It is the ability of a cation to attract the electron cloud towards itself. Electronegativity : The tendency of an atom to attract the shared pair of electron towards itself. TOPIC-3 Alkaline Earth metals Revision Notes The reactivity of alkaline earth metals towards oxygen increases on going down the group. BeO and MgO are insoluble in water while the other alkaline earth metal oxides are soluble in water to give hydroxide. The alkaline earth metals except Beryllium reacts with water to form corresponding hydroxides with the liberation of hydrogen. The main reason of diagonal relationship between Be and Al is that charge/radius radio of Be2+ ion is nearly same as that for the Al3+ ion. Alkaline earth metals find uses at different places: Beryllium for making windows of X-ray tubes. Radium in the treatment of cancer, etc. Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 33 Know the Terms Halogens : Six non-metallic elements of group 17 or VII A of periodic table. Covalent compounds : The compounds formed due to sharing of valence electrons. TOPIC-4 Compounds of Magnesium and Calcium Revision Notes It occurs as mineral carnallite KCl MgCl2.6H2O The important compounds of calcium are : calcium oxide, calcium hydroxide, calcium carbonate, plaster of Paris etc. Calcium oxide absorbs moisture and carbon dioxide on exposure to atmosphere. Lime stone, marble, Iceland spar, shells of sea animals are some of the forms of calcium carbonate. Cement is one of the most important building materials. It is also known as Portland cement, because on setting it becomes hard like Portland rock. Know the Definitions A suspension of slaked lime in water is known as milk of lime and the clear solution is called as lime water. Know the Terms Precipitated chalk : Also known as calcium carbonate. It is used to reduce acidity in wines. Kilns : a furnace or oven for burning, baking or drying especially one for calcining lime or firing pottery. ll CHAPTER-11 p-BLOCK ELEMENTS TOPIC-1 Group 13 Elements Revision Notes The elements which belong to groups 13, 14, 15, 16, 17 and 18 are called p-block elements. p-block elements are normal or representative elements. Group 13 elements: B, Al, Ga, In and Tl The general electronic configuration of p block elements is ns2np1 6, except Helium. Oxidation state is equal to number of valence electrons. The unique behaviour of the first element is due to absence of d-orbitals. Aluminium is the third most abundant element in the earth s crust. The atomic and ionic radii of group 13 elements are smaller than those of the corresponding elements of group 2. The melting and boiling point of boron are much higher as compared to the other elements of the group. The melting point of group 13 elements decreases from B to Ga and then increases up to Tl. 34 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI Boron trihalides act as Lewis acids. The relative order is : BBr3 > BCl3 > BF3 The acidic character of oxides and hydroxides of group 13 elements decreases on moving down the group. Oxides : B2O3 Al2O3 Ga2O3 In2O3 Tl2O3 Hydroxides : B(OH)3 Al(OH)3 Ga(OH)3 In(OH)3 Tl(OH)3 weekly amphoteric amphoteric basic basic acidic Know the Definitions The reluctance of the valence shell s-electron pair to get unpaired and to participate in bond formation is called inert pair effect. Know the Terms Lewis acids: Any substance such as H+ ions that can accept a pair of non- bonding electrons. TOPIC-2 Some important compounds of Boron Revision Notes Boron does not occur in free state in nature. Diborane is an electron deficient compound. It shows three centered two electron bonding. On heating, borax loses its water of crystallization and swells up into a white opaque mass. On further heating at 1013K, the anhydrous mass fuses and forms a transparent glassy mass. Orthoboric acid (H3BO3) possesses a layer structure. It has planar BO3 units linked together through hydrogen bonds, Each H atom acts as a bridge between two oxygen atoms of two adjacent BO3 units. Practically, there is no action of dil. or conc. HNO3 on aluminium. However, nitric acid renders it passive by making a protective film of oxide (Al2O3) on the surface of the metal. Aluminium dissolves in caustic alkalis like NaOH, KOH etc. with the liberation of dihydrogen. Aluminium is used for thermite welding as it acts as strong reducing agent. It reduces many metallic oxides to the respective metal. Anhydrous aluminium chloride is prepared by passing dry chlorine gas over heated aluminium powder. On heating at 473K, potash alum swells and loses all of its water of crystallization. The anhydrous alum obtained is called burnt alum. Know the Terms Anhydrous : containing no water TOPIC-3 Group 14 elements Revision Notes Group 14 Elements : C, Si, Ge, Sn and Pb The melting and boiling points of C and Si are much higher as compared to other elements of the group due to presence of strong intermolecular forces of attraction. Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 35 Carbon and silicon exhibit a great tendency to form covalent compounds in which they show tetravalency. The hydrides of carbon are called hydrocarbons. The acidic nature of dioxides of group 14 decreases down the group Carbon dioxide (CO2) is a gas at room temperature, whereas the dioxides of the other elements are network solids. Diamond sp3 hybridization Graphite sp2 hybridization Graphite is a good conductor of electricity because each C-atom possesses sp2 hybridization and utilizes one 2s and two 2p-orbitals for bond formation. The third 2p-orbital with an unpaired electron is free to delocalize, which is responsible for conduction of electricity in graphite. With hot and dilute HNO, carbon forms a brown substance called artificial tannin. While, with conc. HNO3, it gets oxidised to CO2. Know the Definitions Allotropy : The phenomenon in which an element exists in different forms having different physical properties but similar or almost similar chemical properties. Know the Terms Inert pair effect: The inert pair effect is the reluctance of s-electrons to take part in bond formation Fajan s rule: The rule predicts whether the chemical bond will be covalent or ionic. TOPIC-4 Carbon and its compounds Revision Notes Silicon carbide (SiC) is commonly known as Carborundum. Silicones are organo silicon polymers having repeated R2SiO units held together by Si O Si linkages. They are the metal derivatives of silicic acid ,H2SiO4. Know the Definitions Water gas : A mixture of CO and hydrogen is known as water gas. Silicones : Silicones are synthetic organo silicon polymers containing repeated R2SiO units held together by Si O Si linkages. Fermentation: The chemical breakdown of a substance by bacteria, yeasts or other micro organisms, typically involving effervescence and giving off of heat. Quartz : A hard mineral consisting of silica. Piezo electric material : The materials that produce an electric current when they are placed under mechanical stress. ll 36 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI CHAPTER-12 ORGANIC CHEMISTRY TOPIC-1 Classification of organic compounds Revision Notes Organic chemistry is the chemistry of carbon compound. F. Wohler (1828) synthesized first organic compound urea in the laboratory from inorganic compound which discarded vital force theory given by Berzelius. Kolbe (1845) synthesized acetic acid from its constituent elements. Catenation is the property of atoms of an element to link with one another by stable covalent bonds to form straight chains, branched chains or rings. Ring Branched chain Straight chain C C C C C C C C C C C C When two or more compounds have same molecular formula but differ in structure, then this phenomenon is called isomerism and such compounds are called isomers. Carbon atom is tetravalent in nature. The formation and shape of molecules like methane CH4, ethane C2H6 ,ethylene, C2H4, acetylene C2H2 can be explained on the basis of sp3, sp3, sp2 and sp hybridisation respectively. The different ways to represent organic compounds are: H H H H H C C C C H isobutane bond line notation H H H H n-butane Graphic formula CH3 CH = CH 2 structural formula CH3CHCH 3 condensed structural formula To represent three-dimensional structure of organic molecules, the solid wedge ( ) is used to represent a bond projecting out of the plane of paper towards the observer and the dashed wedge ( ||||||||| ) is used to represent the bond projecting out of the plane of paper away from the observer. The important type of molecular models are : (i) Framework model (ii) Ball and stick model (iii) Space filling model. Saturated hydrocarbons contain single covalent bonds. e.g. H H H C C H H H ethane [ 37 Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI Unsaturated hydrocarbons contain one or more double or triple bond between carbon atoms. e.g., H H H C C H C=C ethyne H H ethene Carbon atoms present in an alkane can be classified into following categories: CH 4 CH3 CH3 1o Secondary carbon atoms : 1o 1o CH3 CH 2 CH3 1o Tertiary carbon atom : 2o 1o 3 1 1 CH3 CH CH3 CH3 1 Quaternary carbon atom : 1 CH3 1 4 1 CH3 C CH3 CH3 1 Functional group : R H Hydrocarbon H +X R X organic compound or aliphatic compounds, R is an alkyl group. F For Aromatic compounds, R is a benzene nucleus. Organic compounds with same functional group behave similarly. Some of the important functional group: Functional group Name of functional group Corresponding family -X Halo halogen compounds -OH Hydroxyl alcohols -O-R alkoxy ethers -CHO formyl (aldehydic group) aldehydes -COOH carboxyl carboxylic acid -NH2 amino amines -CONH2 amide amides A functional group is defined as an atom or group of atoms which decides the mode of activity of a given compound. According to homologous series, the two consecutive members differ by CH2 group in their molecular formula. IUPAC = International Union of Pure and Applied Chemistry. For writing the IUPAC name of compound, the following arrangement should be followed: Prefix(es) + Word Root + Primary suffix + Secondary Suffix. I. Word roots for different carbon chains Chain length Word root C1 Meth- C2 Eth - C3 Prop- C4 But - C11 Undec- C20 Icos 38 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI II. Primary suffix: Nature of carbon chain Primary suffix General name Saturated (C C) -ane alkane unsaturated having one double bond (C = C) -ene alkene Unsaturated having one triple bond -yne alkyne III. Secondary suffix: Class of organic compounds Functional group Secondary suffix Alcohol -OH -ol Aldehyde -CHO -al Carboxylic acid -COOH -oic acid Acid chloride -COCl -oyl chloride Amide -CONH2 -amide Nitrile -CN -nitrile The presence of a functional group is indicated by adding a particular suffix for functional group. A few examples as shown below: O Carboxylic acid R OH -oic acid O Ester R OR' -oate O Amide Nitrile R NH2 R C N -amide -nitrile O Aldehyde R H -al O Ketone R R1 -one Alcohol R OH -ol Amine R NH2 -amine Alkene R2C = CR2 -ene Alkyne RC CR -yne If the group contains carbon (eg. CHO, COOH). The carbon atom of group should also be included while numbering carbon atoms in the parent chain. The numbering of the longest chain is done from the end from which the principal group is nearer. Bond line notation is simple and convenient method to represent an organic compound. Know the Definitions The branch of chemistry which deals with the study of hydrocarbons and the compounds which could be thought of as the derivatives of hydro carbons is called organic chemistry. Catenation : The property of atoms of an element to link with one another by stable covalent bonds to form straight chain, branched chain or rings is called catenation. Isomerism : When two or more compounds having the same molecular formulae possess either different chemical structures or different arrangement of atoms in space, the phenomenon is called isomerism and such compounds are referred to as isomers. IUPAC : International Union of Pure and Applied Chemistry. Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 39 TOPIC-2 Nomenclature of Aromatic compounds Revision Notes The term aromatic has been derived from the Greek word aroma which means sweet smelling. Aromatic hydrocarbon is referred to as arenes. In monosubstituted derivatives, the substituent group is at 1 position. The 1, 2 derivative is termed as ortho; 1, 3 derivative as meta; 1, 4-derivative as para derivative. 1, 2, 3-derivative is termed as vicinal; 1, 2, 4-derivative is termed as asymmetrical; 1, 3, 5-derivative is termed as symmetrical derivative. The term isomerism was first used by Berzelius. Two types of stereo isomerism is : Geometrical and optical. Geometrical isomerism is shown by the compounds of type : ab C = Cab or a x C =Cay, where a, b, x and y represent atoms or groups attached to carbon atoms. The main cause of geometrical isomerism is the restricted rotation of carbon atoms. Geometrical isomers have different physical properties like melting points, boiling points etc. Trans-isomers are more stable as compared to the corresponding cis-isomers. Know the Definitions Isomerism : When two or more compounds having the same molecular formula differ in physical or chemical properties, the phenomenon is known as isomerism and such compounds are called as isomers. Structural isomerism : When the isomers have the difference in chemical structures. Stereo isomerism : When the isomers have different spatial arrangements of atoms or groups. When two or more compounds having the same molecular formula possess different chemical structures on account of different arrangements of atoms in their molecules, the phenomenon is known as structural isomerism. When two or more compounds having the same molecular formulae possess different arrangement of carbon atoms in the main chain, the phenomenon is known as chain isomerism. When two or more compounds having the same molecular formula possess different positions of double bond, triple bond or functional group the phenomenon is known as position isomerism. Functional isomerism : When two or more compounds having the same molecular formula contain different functional groups, the phenomenon is known as functional isomerism. Metamerism: When two or more compounds having the same molecular formula and the same functional group possess different types of alkyl groups attached on both sides of the functional group, the phenomenon is known as metamerism. Ring chain isomerism: When two or more compounds having the same molecular formula differ in the mode of linking of carbon atoms and have open chain and closed chain structures, the phenomenon is known as ring chain isomerism. Tautomerism: It is a phenomenon in which a single compound exists in two readily interconvertible forms which differ markedly in the relative position of atleast one atomic nucleus, generally hydrogen. When two or more compounds having the same molecular formula and similar chemical structures, possess different arrangements of atoms or groups in space and possess different properties characteristics of their configuration , the phenomenon is known as stereo isomerism and such compounds are called stereo isomers. TOPIC-3 Optical Activity Specific rotation is defined as the number of observed degree of rotation caused by an optically active compound when plane polarized light is passed through 1 dm of its solution having concentration of one gm ml 1. When an object is non superimposable on its mirror image, it is said to be chiral. A carbon atom having four different atoms or groups is called an asymmetric carbon or chiral carbon. 40 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI A molecule is said to be chiral or dissymmetric when it does not have any kind of symmetry Chirality is regarded as the necessary condition for a molecule to be optically active. Racemic mixture (dl-mixture) is the mixture having equimolar concentration of d and l-isomers of a substance. Racemic mixture is optically inactive due to external compensation. The process of separation of a racemic mixture into its d and l form is called resolution. Asymmetric synthesis involves synthesis of asymmetric compound (optically active) from a symmetric compound (optically inactive). Meso form is optically inactive due to presence of plane of symmetry i.e. internal compensation. Know the Definitions When a substance rotates plane of polarized light in clockwise direction or anticlockwise direction, then this phenomenon is called optical activity and the substance is called optically active compound. The instrument which measures optical activity of a substance is called polarimeter. The property of a substance of rotating the plane of polarised light through a definite angle is called optical activity. The stereo isomers which are the non- super imposable mirror images of each other are termed as enantiomers. When two or more compounds have same molecular formula and similar chemical structure show different effects on plane polarised light, then this phenomenon is called optical isomerism and such compounds are called optical isomers. The process by which racemic mixture is obtained from d and l-forms of an optically active substance is called racemization. The optical isomers of a compound which are not the mirror images of each other are called diastereomers and this phenomenon is called diastereoisomerism. TOPIC-4 Detection of elements Revision Notes Copper oxide is hygroscopic in nature. There is no satisfactory qualitative test for oxygen. Nitrogen can be detected by Lassaigne s test. If an organic compound contains nitrogen, a Prussian blue colour is obtained during its test. If an organic compound contains both N and S, a blood red colouration is obtained in above test. Sodium extract contains sodium cyanide or sodium sulphide along with sodium halide. Carbon and hydrogen can be estimated by Liebig s method. Nitrogen can be estimated by Duma s method and Kjeldahl s method. Carius method is used for estimation of halogen in organic compounds. Sulphur can be estimated by Carius method. Know the Formulae %N = 28 Volume of N 2 at STP 100 22400 x mass of the compound % of C = 12 Mass of CO2 formed 100 44 x mass of the compound % of H = 2 Mass of water formed 100 10 x mass of the compound Molecular mass of acid = equivalent mass of an acid basicity of the acid. Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 41 Molecular mass of base = equivalent mass acidity n = molecular mass Empirical formula mass Molecular formula = n empirical formula Know the Terms Alkali : a base that dissolves in water. Pyrolyzed: it is a process of chemically decomposing organic materials at elevated temperature in the absence of oxygen. TOPIC-5 Types of chemical Reactions and their mechanism Revision Notes Substrate + attacking agent product If both inductive and electromeric effects are operative in the same molecule, but in opposite direction, the electromeric effect usually dominates the inductive effect. Hyper conjugation is also termed as no bond resonance. The atom taking away both the shared electrons is more electronegative. The two type of attacking reagents common in organic reactions are : Electrophilic reagents. Nucleophilic agents Know the Terms The sequence of steps depicting the cleavage of old bonds in substrate molecules and formation of new bonds leading to the formation of products through reaction intermediates is called reaction mechanism. The displacement of s-electrons along a saturated carbon chain due to the presence of an electron withdrawing or electron repelling group at one end of the chain resulting in the development of partial positive or negative charges in the decreasing order of magnitudes is called inductive effect. (-I effect) The complete transfer of shared pair of p-electrons of a multiple bond to one of the shared atoms in the presence of an attacking reagent is called Electromeric effect. The phenomenon in which a molecule is represented by several electronic structures which do not differ much in their energy contents and are obtained by oscillations of p-electrons is called resonance. The difference between the energy content of the resonance hybrid and the energy content of the canonical structure possessing least energy is termed as resonance energy. Hyperconjugation involves delocalization of s electrons of C H bond of an alkyl group directly attached to an atom of unsaturated system. Bond Fission Heterolytic Fission Homolytic Fission In homolytic fission, one of the electrons of the shared pair in a covalent bond goes with each of the bonded atom. A : B A: + B + Heterolytic fission In heterolytic fission, the bond breaks in such a manner that the shared pair of electrons remains with one of the fragments. A B Light Energy A + B Homolytic fission 42 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI A free radical may be defined as an atom or group of atoms having an unpaired electron. Carbocation may be defined as the positively charged species in which the central carbon atom contains positive charge with six bonding electrons. Carbanion may be defined as the negatively charged species in which the central carbon atom contains negative charge with six bonding electrons and one unshared pair of electrons. A reagent that takes away an electron pair from reactive site is called electrophile (E+) . It is an electron deficient species. A reagent that brings an electron pair to there active site is called nucleophile (Nu :). It is an electron rich species. The reactions which involve the direct replacement of an atom or a group by atoms by some other atom or a group of atoms are called substitutions reactions. The reaction in which a reagent is added at the site of a multiple bond present in a substrate is called addition reaction. The reaction which involve the elimination of a molecule from the substrate molecule leading to the formation of a multiple bond is called elimination reaction. The reaction which involves a rearrangement of atoms or groups in the substrate molecule to form a structural isomer is called rearrangement reaction. ll CHAPTER-13 HYDROCARBONS TOPIC-1 Classification of Hydrocarbons Revision Notes Hydrocarbons are the organic compounds made of only carbon and hydrogen atom. (Aliphatic hydrocarbon) cycloalkanes (aliphatic) Alkanes are saturated hydrocarbons which are also called paraffins. (In Latin parum + affins meaning little affinity). The general formula of alkanes is CnH2n+2. The Staggered conformer is relatively more stable than the eclipsed or skew conformers. The stability of a conformation depends upon the repulsive interaction between the electron cloud. This repulsive interaction is called torsional strain. Greater the branching of the chain in alkane, lower is the boiling point of the isomers. Alkanes are prepared by following methods: From unsaturated hydrocarbons From alkyl halides From carboxylic acid Alkanes are highly combustible in nature. The decomposition of a compound by heat is called pyrolysis or thermal decomposition. Pyrolysis of alkanes is a free radical reaction. Uses : Methane is used in the manufacture of hydrogen. Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 43 Know the Definitions The different spatial arrangements obtained by the free rotation around the bond axis of a C-C s bond is called conformers or rotamers and the molecular geometry corresponding to a conformer is known as conformation. Isomerisation : The process of conversion of one isomer into some other isomer is termed as isomerisation. Aromatisation : The process of conversion of aliphatic compounds into aromatic compounds is known as aromatisation. Know the Terms Unsaturated hydrocarbon: Hydrocarbon that have double or triple covalent bonds between adjacent carbon atoms. Intermolecular force: Intermolecular forces are force of attraction or repulsion which act between molecules. Non polar covalent compounds: It is a type of bond that occurs when two atoms share a pair of electrons with each other. TOPIC-2 Alkenes and alkynes Revision Notes Alkenes are unsaturated hydrocarbons containing one or more double bond. Removal of water molecule from a compound is termed as dehydration. Dehydrohalogenation is the process of removal of a molecule of hydrogen halide from a compound. The rate of b-elimination for halogens, iodine > bromine > chlorine and for alkyl group is 3o > 2 o > 1 o Dihalogen derivatives of alkenes in which two halogen atoms are present on the neighbouring carbon atoms are called as vicinal dihalides. The boiling point of alkenes increase with increase in molecular weight. Know the Definitions Geometrical isomerism: When two compounds having the same molecular formula, similar chemical structures and a double bond possess different geometrical arrangement of the atoms or groups about the doubly bonded carbon atom, the phenomenon is known as geometrical isomerism. Dehydration: Removal of water molecule form a compound is known as dehydration. Dehydrohalogenation: It is the process of removal of a molecule of hydrogen halide from a compound. Vicinal dihalides: Di halogen derivatives of alkenes in which the two halogen atoms are present on the neighbouring carbon atoms are called as vicinal dihalides. Hydrogenation: Addition of hydrogen is called as hydrogenation. Markovnikov s rule: During the addition of an unsymmetrical reagent of the type HX to an unsymmetrical alkene, the negative part of the reagent goes to that carbon which carries smaller number of hydrogen atoms whereas the positive part of the reagent gets attached to that carbon which contains larger number of hydrogen atom. Anti Markovnikov s rule or Kharasch peroxide: When HBr is added to an unsymmetrical alkene in presence of an organic peroxide R-O-O-R such as benzoyl peroxide the addition takes place against the Markovnikov s rule. Polymerization : When a large number of molecules combine together to form a large molecule of very high molecular mass under suitable experimental conditions, the process is known as polymerization. 44 ] Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI TOPIC-3 Aromatic Compounds Revision Notes The unsaturated hydrocarbons containing one or more benzene rings are called aromatic hydrocarbons. They are also known as arenes. Kekule explained that the double bond in benzene ring were continuously oscillating back and forth between the neighbouring carbon atom. The unique behaviour of Benzene and its derivatives in comparison to its aliphatic compounds are termed as aromaticity. Ortho and para directing groups: Meta directing groups: NO2, C N, SO3H, CHO, COOH The substituents which enhance the rate of second substitution with respect to benzene are called activating substituents (o and p directing substituents). The substituents which decrease the rate of second substitution with respect to benzene are called deactivating substituents (m directing substituents). Some deactivating substituents ( F, Cl, Br, I) are o- and p-directing. Benzene is the most important arene. Benzene can be prepared from sodium benzoate and phenol. Halogenation in benzene takes place in the presence of Lewis acid. Fuming sulphuric acid is conc. sulphuric acid containing dissolved SO3. Benzene burns with a smoky flame to give carbon dioxide and water. Chlorination of benzene occurs in the presence of UV light. The hydrocarbons containing two or more fused benzene rings are called poly nuclear hydrocarbons. Coal tar is the main source of poly nuclear hydrocarbons. Know the Definitions A ring system exhibits aromatic nature when it contains (4n + 2) electrons, where n = 1, 2, 3 etc. It is called Huckel rule. Know the Terms BHC : Benzene hexa chloride ll CHAPTER-14 ENVIRONMENTAL CHEMISTRY Revision Notes Environmental pollution occurs by the effect of undesirable changes in our surroundings that have harmful effect on plants, animals and human beings. A substance which causes pollution is called pollutant. The lowest region of the atmosphere in which the human beings along with other organisms live is called troposphere. Oswaal ISC Chapterwise & Topicwise Revision Notes, CHEMISTRY, Class XI [ 45 The Ozone is present in the stratosphere which protects about 99.5% of the sun s harmful UV radiations from reaching the earth s surface. The substance which readily degrades in natural environment by micro-organisms are called biodegradable pollutants. The undesirable changes in physical, chemical and biological properties of air which harmfully affect the living creature lead to air pollution. Atmospheric pollutants are either gaseous or particulate in nature. 1ppm of Sulphur trioxide is also harmful for humans. Smog is a mixture of smoke and fog in suspended droplet form. Acid rain refers to the presence of excessive acids (H2SO4, HNO3 etc.) in rain water. The pH of acid rain is less than 5.6. Ozone layer is depleted by Nitric oxide Atomic oxygen Hydroxy radical Chlorofluoro carbon(CFC) The depletion of ozone layer leading to the formation of ozone hole is hazardous to human health. The progressive warming up of the earth s surface due to blanketing effect of man made CO2 is called greenhouse effect. The gases responsible for greenhouse effect are called greenhouse gases. The greenhouse gases are carbon dioxide, methane, nitrous oxide, CFC , ozone and water vapours. The main gas responsible for greenhouse effect is carbon dioxide. The warming of earth s surface all around us on global level is called global warming. The concentration of dissolved oxygen in water decreases by increases in water pollution. The chemical fertilizers and pesticides in agricultural activities are the major sources of soil pollution. Solid wastes can be managed by proper collection, disposal and recovery of materials. Green chemistry is a production process that would bring about minimum pollution or deterioration to the environment. Know the Definitions Environment may be defined as the sum of all physical ,chemical, biological and even social factors which constitute the surroundings of human beings. Any undesirable change in the physical, chemical or biological nature of air, water and land which directly or indirectly influences the life of man, animals or plants is called pollution. The physical, chemical or biological agents which, when released into the environment already affect the human interests are called pollutants. The pollutants which are emitted directly from the source are called primary pollutants. The pollutants which are formed from primary pollutants are called secondary pollutants. The amount of oxygen required by bacteria to break down the organic matter present in water is called Biochemical Oxygen Demand (BOD). The amount of oxygen required to oxidise polluting substance, including those which are resistant to microbial oxidation is called Chemical Oxygen Demand (COD) of polluted water. The presence of undesirable substances which change the physical , chemical or biological properties of water which cause health hazard is termed as water pollution. The diseases caused by excess fluoride in drinking water is called fluorosis. Green chemistry is a way of thinking and is about utilizing the existing knowledge and principles of chemistry and other science to reduce the adverse impact on environment. ll

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